The present invention relates generally to winches of the planetary gear type and is more particularly concerned with a planetary gear winch construction comprising a freewheel arrangement for selectively disengaging the winch drum from the power train under no-load conditions.
A planetary gear winch broadly comprises a prime mover coupled to a winch drum through a planetary gear reduction drive train. The planetary gear reduction drive train comprises at least two serial, coacting and coaxially oriented planetary gear reduction stages, each stage comprising a plurality of planet gears journalled in a carrier therefor, said planet gears surrounding and being in engagement with a central sun gear. Each planetary gear reduction stage also comprises a ring gear surrounding and being in engagement with said planet gears, said ring gear acting as a fixed reaction member. While separate and distinct ring gears may be utilized for each planetary gear reduction stage it is conventional to employ a single ring gear of sufficient length to house and serve the entire complement of planetary gear reduction stages, thereby simplify the construction and/or to render it more economic. Rotary power is delivered into each planetary gear reduction stage through the centrally located sun gear thereof. In the case of the first reduction stage, the sun gear is driven by the prime mover. In the case of later stages, the sun gears are each driven by the output of the previous planetary gear reduction stage. The planet gears of each reduction stage are carried in a planet carrier generally comprising a plate member having a plurality of axle stubs extending perpendicularly from one surface thereof and to which axle stubs the planet gears are journalled. Conventionally, the planet carrier for each of the planetary gear reduction stages preceding the final reduction stage also comprises a centrally located sun gear rigidly affixed thereto and extending downstream therefrom, said sun gear acting, as previously mentioned, as the power input member for the suceeding planetary gear reduction stage.
The power output of the final planetary ger reduction stage is coaxially coupled to the winch drum in any suitable manner. For example, the planet carrier of the final planetary gear reduction stage and the bore of the winch drum element can each define a keyway or splined recess, which recesses receive a common suitably conformed key or spline coupling member. As another example, the upstream flange of the winch drum can serve as the planet carrier for the final planetary gear reduction stage, thereby to simplify the construction of said stage and to provide a direct coupling of the output thereof to the winch drum. In this last-mentioned arrangement, axle stubs extend upstream from the upstream winch drum flange and the planet gears of the final reduction stage are journalled thereto. Thus, said planet gears are caused to act as the power output members of the final planetary gear reduction stage driving the winch drum through said axle stubs. Another example of suitable coaxial coupling of a final planetary gear reduction stage to a winch drum is disclosed in U.S. patent application Ser. No. 197,654 Muessel et al., filed Oct. 16, 1980, entitled Rotary Power Coupling and Planetary Gear Winch Comprising Same, now U.S. Pat. No. 4,392,635, July 12, 1983. Therein there is disclosed a flexible coupling arrangement employing an intermediate plateform coupling member whereby the planetary gear train is effectively isolated from racking loads imposed on the winch drum during operations.
It is in the nature of a planetary gear reduction train that the forces required to drive the train in reverse, when applied rearwardly through the final reduction stage of the gear train, are relatively great. This inherent characteristic of planetary gear reduction trains is employed to advantage in winch applications in that, when the prime mover is inactivated, the planetary gear train acts to produce a substantial braking of the winch drum against reverse rotation thereof under line load. Where the load capacity of the winch is substancial it is also conventional to provide various supplemental mechanical and/or electrical braking systems to mitigate against unintentional reverse rotation of the winch drum upon shutdown of the prime mover. Generally speaking, such supplemental braking systems are located upstream from the planetary gear train thereby to ensure that full use is made of the inherent braking effects of the planetary gear reduction train and to minimize the bulk and complexity required of the supplemental braking system.
In many planetary gear winch applications it is highly desirable that the winch be provided with means by which the winch drum, in the unloaded condition, can be temporarily disconnected from the drive train therefor, thereby to be rendered freely rotatable and to allow rapid unwinding of the line therefrom. This is a particularly desirable feature, for instance, in connection with off-the-road vehicle and boat trailer winch applications wherein a lone operator may be called upon to deploy the line from the winch drum, affix it to a fixed object or to a load and place the winch in operation. In accordance with the present invention, a winch construction comprising such selectively operable freewheel arrangement is provided.